Anaerobic Ammonium Oxidation Sludge Research Articles

Microbial interactions play a keystone role in rapid anaerobic ammonium oxidation sludge proliferation and biofilm formation

Two mature anaerobic ammonium oxidation (anammox) consortia with high/low relative abundance of anammox bacteria were inoculated for the rapid sludge proliferation and biofilm formation in this study, named up-flow anaerobic sludge blanket reactor (UASB1) (high) and UASB2 (low), respectively. Results showed that the nitrogen removal efficiency of UASB2 reached 90.94% after the 120-day operation, which was 13% higher than that of UASB1. Moreover, its biomass amounts were 22.18% (biofilm) and 40.96% (flocs) higher than that of UASB1, respectively. Ca. Kuenenia possessed relative abundances of 29.32% (flocs), 27.42% (biofilm) and 31.56% (flocs), 35.20% (biofilm) in the UASB1 and UASB2, respectively. The relative abundances of genes involved in anammox transformation (hzs, nir) and carbon metabolism (fdh, lgA/B/C, acs) were higher in the UASB2, indicating that Ca. Kuenenia might produce acetate and glycogen to enhance microbial interactions. These findings emphasized the importance of microbial interactions in anammox sludge proliferation and biofilm formation.

Initiating an anaerobic ammonium oxidation reactor by inoculation with starved anaerobic ammonium oxidation sludge and modified carriers

Prolonged starved anammox sludge (SAS) obtained during initial rejuvenation was inoculated into a reactor together with activated sludge (AS), anaerobic granular sludge (AGS) and modified carriers consisting of honeycomb carrier with high biological interception and activated carbon carrier with high adsorption performance. SAS accounted for 5% of the inoculated sludge. The anammox process was started and operated at around 25℃. After 160 days, the nitrogen loading rate and nitrogen removal rate reached 1.12 kgN·m−3·d−1 and 0.97 kgN·m−3·d−1, respectively. Obvious red anammox biofilms were observed on the modified carriers. Microbial community analysis showed that the relative abundance of anammox bacteria increased from < 0.1% to 22.96%. Candidatus Jettenia and Candidatus Brocadia were the dominating anammox species. This work demonstrates the potential to reuse SAS to improve the start-up efficiency of anammox reactors, which makes good economic sense.

Fast Start-Up ANAMMOX Operation Strategy and Flora Characteristics of a Biofilter

To achieve the rapid start-up of anaerobic ammonia oxidation (ANAMMOX) reaction at room temperature and sludge granulation, a small amount of ANAMMOX sludge was inoculated by an upflow biological filter reactor, and ANAMMOX was started by stage variable load and shortening hydraulic residence time (HRT) operation strategy. The reaction was evaluated, and the nitrogen removal characteristics of the biofilter were evaluated. The results showed that the biofilter started the ANAMMOX reaction in a medium-temperature (25-29℃) environment for 22 days. After 97 days of culture, the total nitrogen volume removal rate (NRR) reached 5.64 kg·(m3·d)-1, the total nitrogen (TN) removal rate was close to 80%, and the average particle size of the granular sludge was 4.5 mm. High-throughput sequencing analysis showed that the biofilter formed a layered structure of nitrifying bacteria-heterotrophic bacteria, anaerobic ammonium oxidation bacteria (AAOB), and AAOB-heterotrophic bacteria from bottom to top. The various microflora synergistically denitrified, creating a low dissolved oxygen (DO) stable environment for AAOB, and the dominant population Candidatus Kuenenia (AF375995.1) was enriched. In addition, the removal process of pollutants along the path and the characteristics of sludge along the process were analyzed, and it was verified that the sludge in the reaction zone had good ANAMMOX activity. An ANAMMOX-biofilter reactor achieves rapid start-up of the ANAMMOX reaction, sludge granulation, and efficient operation by effectively maintaining the amount of bacteria and stabilizing the reaction conditions.

Effect of Hydroxylamine on Community of ANAMMOX Sludge

At present, the anaerobic ammonium oxidation (ANAMMOX) process has the advantages of high efficiency, low energy consumption, and low sludge quantity, and it therefore has broad application prospects in sewage nitrogen removal. Hydroxylamine is not only an intermediate product of ANAMMOX metabolism but also an inhibitor. However, the effect of hydroxylamine on the activity of ANAMMOX is not clear. Therefore, we investigated the ANAMMOX activity under the condition of adding different concentrations of hydroxylamine (40-80 mg·L-1) through a hydroxylamine batch experiment. It was found that hydroxylamine can inhibit ANAMMOX activity. However, it was impossible to determine the threshold of ANAMMOX bacteria to hydroxylamine. Next, the mRNA levels of hydrazine oxidase (HZO) in different reactors were detected by real-time fluorescent quantitative polymerase chain reaction (RT-qPCR), and it was found that the expression levels of HZO peak and then decrease with an increase of hydroxylamine concentration. It was suggested that the tolerated hydroxylamine concentration was within 60-70 mg·L-1 for 3.12 g·L-1 ANAMMOX granular sludge. Moreover, a 16S rRNA high-throughput sequencing method was used to analyze the structure and function of ANAMMOX granules in microbial communities in the reactor. It was found that the addition of an appropriate concentration of hydroxylamine (50 mg·L-1) helped to enhance the cellular motility of bacteria and promoted the composition of ANAMMOX bacteria, providing a better ecological balance.

Characteristics of ANAMMOX Granular Sludge and Differences in Microbial Community Structure Under Different Culture Conditions

Anaerobic ammonium oxidation (ANAMMOX) granular sludge was cultured during different operating conditions by an expanded granular sludge bed (EGSB) reactor and up-flow anaerobic sludge bed (UASB) reactors, and the characteristics of the granular sludge and microbial community were compared. The results showed that the flocculent ANAMMOX sludge can be granulated after being operated for 384 days by the EGSB and UASB reactors. The average particle size reached 1.17 mm and 1.21 mm, respectively. The particle size ratio of each range (<0.2, 0.2-1.5, 1.5-3, and>3 mm) was 6.06%, 60.05%, 25.25%, and 8.64% in the EGSB reactor, and 7.40%, 58.90%, 32.04%, and 1.66% in the UASB reactor, respectively. The results of scanning electron microscopy showed that the bacterial flora during different operating conditions were mainly Brevibacterium and Cocci aggregates. High-throughput sequencing results showed that the Shannon index of the EGSB reactor was 7.52, higher than the 7.18 of the UASB reactor on day 384; Proteobacteria was the main phylum of the sludge at each stage, and Planctomycetes increased from 3.30% to 12.30% in the EGSB reactor and 13.30% in the UASB reactor on day 384. The main ANAMMOX genera in the EGSB reactor were Candidatus Brocadia, accounting for 7.53%, followed by Candidatus Kuenenia accounting for 1.61%, whereas in the UASB reactor, Candidatus Kuenenia was the dominant anaerobic ammonia genus, accounting for 7.54%, followed by Candidatus Brocadia, which accounted for 3.69%. The proportion of dominant species was related to the change in environmental factors. The proportion of Candidatus Brocadia was positively correlated with the up-flow rate and nitrogen removal rate (NRR), but negatively correlated with hydraulic retention time (HRT). Candidatus Kuenenia was positively correlated with nitrogen removal efficiency (NRE), NRR, and HRT, but negatively correlated with the up-flow rate.

Rapid Cultivation of Anaerobic Ammonium Oxidation Granular Sludge and Inhibition Kinetics of Granular Sludge

For the rapid cultivation of anaerobic ammonium oxidation (ANAMMOX) granular sludge (AGS), a small amount of flocculent ANAMMOX sludge (FAS) was taken as the research object, and a bio-flow separate ball was used as the filler in an up-flow anaerobic sludge bed (UASB) to rapidly begin ANAMMOX and to cultivate granular sludge. In addition, the substrate inhibition kinetic characteristics of the AGS were investigated by using the Haldane model. The results showed that start-up of the ANAMMOX was successfully achieved. The total nitrogen removal rate was more than 85%, and the volume load of total nitrogen was 0.72 kg·(m3·d)-1. AGS with diameters of 1.0-3.0 mm were cultured within 127 days using the Bio-flow Separate Ball. The kinetic studies showed that the maximum reaction rates for ammonia and nitrite of granular sludge were 1.46 kg·(kg·d)-1 and 1.76 kg·(kg·d)-1, with half inhibition constants of ammonia and nitrite at 852.2 mmol·L-1 and 108.2 mmol·L-1, respectively. Compared with FAS, AGS can withstand higher concentrations of ammonia and nitrite and can maintain a higher reaction rate. The placement of the filler has positive significance for starting ANAMMOX and rapidly culturing AGS.

Extracellular Polymeric Substances of ANAMMOX Granular Sludge and Its Effects on Sludge Surface Characteristics

The anaerobic ammonium oxidation(ANAMMOX) granular sludge in the EGSB reactor was divided into three groups according to particle size, which were R1 (0.5-1.4 mm), R2 (1.4-2.8 mm), and R3 (>2.8 mm). Extracellular polymeric substances (EPS) of different sizes from ANAMMOX granular sludge were extracted, and the EPS characteristics and their influence on the surface characteristics of ANAMMOX aggregates were analyzed. With the increased particle size of ANAMMOX granular sludge, the PS content was between (10.69±0.11)-(12.28±0.15) mg·g-1, while the PN content increased from (56.88±0.86) mg·g-1 to (98.59±2.10) mg·g-1, and PN/PS increased from 5.32 to 9.05. The EPS functional groups and the content of three-dimensional fluorescent components of different size ANAMMOX granular sludge were different. As the granular sludge size increased, the value of α-helix/(β-sheet + random coil) gradually decreased from 0.60 to 0.43, which is beneficial to the hydrophobicity expression of the sludge. Due to the increased particle size of the granular sludge, the hydrophobicity of the sludge surface increased from 54.2% to 63.1%, and the Zeta potential increased from -41.2 mV to -31.5 mV. The increased hydrophobicity and surface charge are beneficial to the formation of sludge aggregates. EPS can enhance ANAMMOX sludge hydrophobicity and increase Zeta potential. The presence of PN in EPS is essential to this process.

Pre-precipitation of Sewage-SNAD Granular Sludge Process Test

Using artificial water, the simultaneous partial nitrification, ANAMMOX (anaerobic ammonium oxidation), and denitrification (SNAD) granular sludge process was started in a sequencing batch reactor (SBR), and then the ammonia concentration in the influent was reduced gradually. After stable operation for a period of time under the low ammonia concentration, sewage treated by a pre-precipitation process was used as a substrate to investigate the performance and stability of the SNAD granular sludge process. The results show that after the SNAD process was successfully started, the ammonia removal rate was greater than 98%, and total the nitrogen removal rate was about 89%. As the influent ammonia concentration decreased, the nitride-oxidizing bacteria (NOB) activity was increased and the total nitrogen removal rate gradually decreased to 75%. When the pre-precipitated domestic sewage (NH4+-N 52-63 mg·L-1, COD 99-123 mg·L-1) was used as the inflow, the average effluent removal rate of the total effluent was 73.2%, the effluent COD concentration was below 35 mg·L-1, and the maximum effluent ammonia nitrogen and total nitrogen concentration were 0.7 mg·L-1 and 12.8 mg·L-1. The ammonia and total nitrogen concentration in the continuous 30 day effluent reached the 1A level of the integrated discharge standard of water pollutants for municipal wastewater treatment, indicating that the removal of organics and nitrogen from domestic sewage was achieved efficiently and synchronously.

Carbon and Nitrogen Removal Characteristics of ABR Decarbonization-CANON Coupling Process

If municipal wastewater can be treated by the completely autotrophic nitrogen removal over nitrite (CANON) process, it will greatly reduce the energy consumption of municipal wastewater treatment. The CANON reactor with a fiber carrier was started up by seeding nitrosation sludge and anaerobic ammonia oxidation (ANAMMOX) sludge in the continuously stirred tank reactor (CSTR). An ABR decarbonization system was added to the front of the CANON system to build the ABR decarbonization-CANON coupling process to examine carbon and nitrogen removal characteristics of the whole system. The high throughput sequencing technology of MiSeq was also employed to analyze the structure of the microbial community before and after the reactivation. The results showed that mixing nitrosation sludge and ANAMMOX sludge in the CSTR reactor under controlled parameters (DO of 0.5-2 mg·L-1; HRT for 6 h; pH of 8) allowed the CANON system to successfully start within 55 d, with a TN removal rate of 81%-87% and ammonia nitrogen load of 0.195 kg·(m3·d)-1. The effluent COD concentration of the ABR decarbonizing system did not adversely affect the subsequent CANON system, and the TN removal rate of the ABR decarbonization-CANON process was between 74% and 87%. Additionally, the average concentration of COD in the effluent was 40 mg·L-1. At the same time, the Proteobacteria gate significantly improved after the CANON system began, and the proportion of Sphingobacteria decreased to 6.8%. Nitrifying bacteria and anaerobic ammonia oxidizing bacteria in the CANON system continuously eliminated the inferior bacterial groups to become the dominant group in the reactor. The integrated ABR decarbonization-CANON process had a positive effect on the denitrification and decarbonization of urban sewage.

A holistic analysis of ANAMMOX process in response to salinity: From adaptation to collapse

The application of anaerobic ammonium oxidation (ANAMMOX) process to industrial wastewater treatment usually faces the challenge of high salinity. However, most of the current ANAMMOX sludge was enriched from low-salinity water, resulting in the critical gap between the inoculum and saline wastewater. In this work, an ANAMMOX reactor fed with inoculum enriched from low-salinity water successfully adapted to saline wastewater (500 mmol/L NaCl, 2.92%) after a long-term stepwise acclimatization. The nitrogen removal rate and total nitrogen removal efficiency reached 9.72 kg·m−3·d−1 and 80.90%, respectively. However, further salinity increase to 600 mmol/L caused a collapse of reactor performance. The proportion of inorganic matters improved along with the increase of salinity, which might be attributed to the compact particles observed in the microstructure of ANAMMOX sludge. A microbial community succession occurred in response to the increase of salinity. When the salinity increased to 160 mmol/L, the dominant functional bacteria shifted from Candidatus Kuenenia to unclassified Brocadiaceae, which was supposed to be salt-tolerant. The up and down regulations of polysaccharides and ζ potential in EPS were positive strategies for salinity adaptation of ANAMMOX bacteria. However, the barrier of seawater salinity (3–5%) could not be overcome. The present work would provide a holistic view for the enrichment of salt-tolerant ANAMMOX bacteria and help in the selection of seeding sludge for the treatment of saline wastewater by ANAMMOX process.

Granular Characteristics of Anaerobic Ammonia Oxidation Sludge During the Recovery Process

Operation instability has become one of the factors restricting the application of the anaerobic ammonia oxidation (ANAMMOX) process. Under the condition that the substrate is not suppressed, the effects of the substrate concentration on the granulation and activity of ANAMMOX granular sludge in the recovery process were studied by restoring the activity of ANAMMOX sludge, which was derived from early-stage operation instability of the continuous stirred tank reactor (CSTR). The results show that the activity of ANAMMOX sludge was recovered and the denitrification capacity increased significantly after 126 days of operation. When the NH4+-N and NO2--N concentrations were 450 mg·L-1 and 560 mg·L-1, respectively, the nitrogen removal was achieved in both the high-and low-substrate concentration reactors and the maximum NRR was 16.97 kg·(m3·d)-1 and 14.43 kg·(m3·d)-1, respectively. With the improvement of the nitrogen removal capacity of the reactor (the granular diameter of the sludge is increased), the extracellular polymeric substance (EPS) content increased in both reactors from 34.45 to 77.52 and to 94.18 mg·g-1, respectively, and the PN/PS increased from 1.89 to 6.25 and 6.84, respectively. To a certain extent, the increase of PN/PS is conducive to the granulation of ANAMMOX sludge, but a too large PN/PS would lead to the instability of granular sludge and sludge loss.

Effect of Substrate Concentration on SAD Collaborative Nitrogen and Carbon Removal Efficiency in an ABR Reactor

In order to solve the problem of declining total nitrogen (TN) removal caused by anaerobic ammonium oxidation (ANAMMOX) and the suppression of organic matter for ANAMMOX, the anaerobic baffled reactor (ABR), inoculating ANAMMOX sludge and anaerobic sludge from a municipal WWTP, was selected to construct system of ANAMMOX coupled denitrification (SAD) by the control of different substrate concentration. The SAD was constructed to study the effects of different influent substrates (COD, NO2--N, NH4+-N) on the performance of nitrogen and carbon removal in the coupled system and pollutant removal rules. The results showed that the coupling reaction was achieved in the ABR reactor and the inhibitory effect of organic compounds on anaerobic ammonium oxidation bacteria (AAOB) was relieved. When influent concentrations of COD, NO2--N, and NH4+-N were 260, 185, and 100 mg·L-1, respectively, which equates to a ratio of 2.6∶1.85∶1, the concentrations of these substances in the effluent decreased to 10, 1.0, and 0.9 mg·L-1, respectively. The TN removal rate reached 99%, hence stable system operation and ultra-low emissions of carbon and nitrogen pollutants were achieved. Under different conditions of substrate concentrations and ratios, the targeted pollutants were generally eliminated in the first compartment, in which the removal rate reached higher than 75%, and ANAMMOX held the dominant position in the SAD coupled system.

Resuscitation of starved anaerobic ammonium oxidation sludge system: Impacts of repeated short-term starvation

Starvation of biomass is common during underloading of bioreactors or sludge storage in biological wastewater treatment industries. The aim of this work was to study the impact of starvation modes on the nitrogen removal capacity of anaerobic ammonium oxidation (anammox) process in sequencing batch reactor (SBR). The repeated short-term starvation and reactivation experiments were performed to evaluate the response of anammox sludge system in the condition of 27 ± 1.5 °C and 320 min HRT. Moreover, the nitrogen removal ability of the anammox process was reactivated rapidly in the low substrate condition, then the total nitrogen (TN) removal efficiency reached 82.5%, with the effluent TN of around 14.6 mgNL−1. The repeated short-term starvation (1 day–4 days) and recovery mode could improve the tolerance and apparent activity of anammox sludge system. The dominant species of general anaerobic ammonium oxidation bacteria (AnAOB) was Candidatus Brocadia, which had better self-adaption to repeated starvation.

Enhancing Nitrogen Removal Performance in a Bioreactor Using Immobilized Anaerobic Ammonium Oxidation Sludge by Polyvinyl Alcohol-Sodium Alginate (PVA-SA)

Enhancing Nitrogen Removal Performance in a Bioreactor Using Immobilized Anaerobic Ammonium Oxidation Sludge by Polyvinyl Alcohol-Sodium Alginate (PVA-SA)

Storage and Reactivation of Anaerobic Ammonium Oxidation (ANAMMOX) Sludge at Room Temperature

Slow growth rates limit the widespread application of anaerobic ammonia oxidation (ANAMMOX) reactions, which presents a need for the study of long-term storage and rapid reactivation of ANAMMOX sludge. Under room temperature conditions (14~30℃), this study investigated the effects of storage duration on the residual activity and the activity after reactivation of ANAMMOX sludge without the addition of external substances. The chosen storage durations were 15, 30, 45, 60, 75 and 100 days, respectively. The results show that the residual specific ANAMMOX activities (SAAs) of the stored ANAMMOX sludge were 90.9%, 64.3%, 61.7%, 43.2%, 25.8% and 19.3% of the initial activity (activity before sludge storage) after 15, 30, 45, 60, 75 and 100 days, respectively. Therefore, the residual SAA decreases linearly with an increase in the storage duration of ANAMMOX sludge (R2 was 0.978). The SAAs after reactivation with a storage duration of 15, 30, 45, 60 and 75 days were all higher than the initial SAA and reached 103.4%, 129.3%, 124.8%, 111.7% and 116.9% of the initial SAA before its storage, respectively. However, the SAA after reactivation after storage for 100 days was just 98.9% of the initial SAA. In conclusion, after as long as 100 days of storage duration under room temperature, the residual SAA of ANAMMOX sludge decreases to 0.0513 g·(g·d)-1, and its ANAMMOX activity can still be recovered after 9.5 days of reactivation culture.

Identification and Influence of Quorum Sensing on Anaerobic Ammonium Oxidation Process

Anaerobic ammonium oxidation (ANAMMOX), an innovative nitrogen removal technology, has good prospects for applications. However, ANAMMOX bacteria grow slowly and are hardly accumulated in bioreactors. In this study, a UASB reactor inoculated with sludge from landfill leachate treatment plant was used for the start-up of ANAMMOX process. Besides, exogenous quorum sensing signals (DSF and AHL) were added to improve the adhesion of ANAMMOX sludge. The results showed that the UASB successfully started the ANAMMOX process within 150 days of operation. The total nitrogen removal rate reached 80% and the proportion of ANAMMOX bacteria rose to 20%. There was a low concentration of AHLs signal molecules in the ANAMMOX sludge. If the β-position substituent group of AHL added was a carbonyl group (including 3-oxo-C6-HSL, 3-oxo-C8-HSL, 3-oxo-C10-HSL and 3-oxo-C12-HSL), the adhesion growth ability of the ANAMMOX sludge could be improved. In the case of dosing with AHL molecules without β-position substituent groups, only C6-HSL and C12-HSL could promote the adhesion of ANAMMOX sludge. The additions of C8-HSL, C10-HSL and DSF all had negative effects on the adhesion of ANAMMOX sludge.

The Nitrogen Removal Performance about ANAMMOX Sludge Immobilized in Polyvinyl Alcohol (PVA) Gel

This study evaluated the use of PVA gel to encapsulate slow-growing anaerobic ammonia oxidation (ANAMMOX) bacteria for deammonification in wastewater treatment. Different kinds of granules with ANAMMOX sludge immobilized in PVA gel in different mass concentration 6%, 10%, 15%, 20% were prepared by cross-linking in calcium chloride solution and nitrogen removal experiments were carried out. The results showed that 10% was the best concentration for ANAMMOX sludge to be immobilized in PVA gel when better nitrogen removal performance with ammonia removal rate (ARR) and nitrite removal rate (NIRR) reaching up to 90% and mechanical strength were estimated synthetically. The tolerance experiments in salt-containing waste water showed that the immobilized granules had the better tolerance than ANAMMOX sludge.

Inhibition kinetics and granular sludge in an ANAMMOX reactor treating mature landfill leachate.

The present study reports the inhibition kinetics and granular sludge in an anaerobic ammonium oxidation (ANAMMOX) - up-flow anaerobic sludge blanket reactor fed with diluted mature landfill leachate. The activity of ANAMMOX bacteria was inhibited by addition of mature landfill leachate, but gradually adapted to the leachate. The system achieved efficient nitrogen removal during 65-75 d and the average removal efficiencies for NH4+-N, NO2--N and total nitrogen (TN) were 96%, 95% and 87%, respectively. ANAMMOX was the main pathway of nitrogen removal in the system, and heterotrophic denitrification occurred simultaneously. In addition, aerobic ammonia oxidation and aerobic nitrite oxidation were active in this system. Inhibition kinetic experiments showed that the NH4+-N and NO2--N inhibition concentration threshold of ANAMMOX were 489.03 mg/L and 192.36 mg/L, respectively. ANAMMOX was significantly inhibited by mature landfill leachate, and was completely inhibited when the leachate concentration was 1,450.69 mg/L (calculated in chemical oxygen demand). Thus, the inhibition concentration of substrate and landfill leachate should be considered when applying the ANAMMOX process to landfill leachate. The color of granular sludge ANAMMOX changed from brick-red into a reddish-brown. The particle size increased from small to large, with evident granulation of the ANAMMOX sludge.

Applying low frequency ultrasound on different biological nitrogen activated sludge types: An analysis of particle size reduction, soluble chemical oxygen demand (SCOD) and ammonia release

Applying low frequency ultrasound could effectively pretreat waste activated sludge (WAS) undergoing anaerobic digestion (AD), because the ultrasound can break up the flocs and cell walls. In this study, we applied ultrasound to three types of biological nitrogen activated sludge in an ice bath. Power densities ranged from 0 to 1.30 W mL−1 and reaction times ranged from 0 to 30 min. The three types of sludge included: short-cut nitrification denitrification sludge (SCND-SBR), complete nitrification denitrification sludge (CND-MUCT), and anaerobic ammonium oxidation sludge (AMX-SHARON). Experiments showed that reductions in average particle size were significantly decreased, due to breakage, at an ultrasonic duration of 10 min with different energy densities. More soluble chemical oxygen demand (SCOD) was detected when the ultrasonic density was higher and the duration was shorter, compared to when the density was lower and the duration was longer. Results suggest that ultrasonic density has a greater impact on the SCOD disintegration degree (DDCOD) as compared to operation time. Soluble proteins (SP) and NH4+N were released during the ultrasound; however, this process does not inhibit the subsequent methanogenic activity during the AD process. The ultrasonic density of 1.04 W mL−1 was the most economic and effective, with the highest efficiency in reducing particle size and releasing SCOD. Therefore, applying ultrasound can accelerate the hydrolysis rate, a rate-limiting factor during AD. This may ultimately reduce treatment construction and operational costs.

Performance and hydrodynamic features of a staged up-flow ANAMMOX sludge bed (SUASB) reactor

• The staged ANAMMOX reactor (SUASB) was investigated systematically. • The application of the kinetic model was validated. • The robust performance of the SUASB was demonstrated. • A maximum NRR of 6.04 kg N m −3 d −1 and NLR of 6.88 kg N m −3 d −1 were achieved. • The hydrodynamic type of the SUASB reactor was investigated. The performance and hydrodynamic features of a staged up-flow ANAMMOX (anaerobic ammonium oxidation) sludge bed (SUASB) reactor was evaluated. When the reactor was at steady-state conditions, the nitrogen loading rate (NLR) and nitrogen removal rate (NRR) were 5.63 and 4.82 kg N m −3 d −1 , respectively. The reactor could withstand a 1.5-fold substrate or hydraulic shock. The modified Stover–Kincannon model was used for the kinetic analysis, and the saturation value ( K B ) and maximum total substrate utilization rate ( U max ) were 14.5 and 14.8 kg N m −3 d −1 , respectively. Moreover, the C ( t )– Θ curve showed the existence of dead zones in the SUASB at the hydraulic retention times (HRTs) of 3 and 12 h, and the flow pattern performance of the SUASB fell between those of a continuous stirred tank reactor (CSTR) and a plug flow reactor (PFR).